Twiggy froggy foam replacement

[ried]

One of my Twiggy drives had a disk inserted and clamped while powered down for several decades - which has permanently compressed the foam by a significant amount (maybe 30-50%?). While the drive is clean and works, it is unreliable and my suspicion is that the froggy's compressed foam is a contributing factor - not providing enough clamping force as originally designed.

Does anyone know the froggy foam specs and what may serve as a suitable replacement? The two pieces are illustrated in the Twiggy manufacturing instructions PDF available from Bitsavers, but no details are provided.